Free-run Stop
A method of stopping a motor, caused when the inverter simply turns
OFF its motor output connections. This may allow the motor and load
to coast to a stop, or a mechanical brake may intervene and shorten
the deceleration time.
Frequency Setting
While frequency has a broad meaning in electronics, it typically
refers to motor speed for variable-frequency drives (inverters). This is
because the output frequency of the inverter is variable, and is
proportional to the attained motor speed. For example, a motor with a
base frequency of 60 Hz can be speed controlled with an inverter
output varying form 0 to 60 Hz. See also
Base Frequency, Carrier
Frequency, and Slip.
Harmonics
A
harmonic is a whole number multiple of a base of fundamental
frequency. The square waves used in inverters produce high
frequency harmonics, even though the main goal is to produce lower-
frequency sine waves. These harmonics can be harmful to electronics
(including motor windings) and cause radiated energy that interferes
with nearby electronic devices. Chokes, line reactors, and filters are
sometimes used to suppress the transmission of harmonics in an
electrical system. See also
Choke.
Horsepower
A unit of physical measure to quantify the amount of work done per
unit of time. You can directly convert between horsepower and Watts
as measurements of power.
IGBT
Insulated Gate Bipolar Transistor(IGBT) – A semiconductor
transistor capable of conducting very large currents when in
saturation and capable of withstanding very high voltages when it is
OFF. This high-power bipolar transistor is the type used in Hitachi
inverters.
Inertia
The natural resistance a stationary object to being moved by an
external force. See also
Momentum.
Intelligent Terminal
A configurable input or output logic function on the Hitachi
inverters. Each terminal may be assigned one of several functions.
Inverter
A device that electronically changes DC to AC current through an
alternating process of switching the input to the output, inverted
and non-inverted. A variable speed drive such as the Hitachi L200 is
also called an inverter, since it contains three inverter circuits to
generate 3-phase output to the motor.
Isolation
Transformer
A transformer with 1:1 voltage ratio that provides electrical isolation
between its primary and secondary windings. These are typically
used on the power input side of the device to be protected. An
isolation transformer can protect equipment from a ground fault or
other malfunction of nearby equipment, as well as attenuate
harmful harmonics and transients on the input power.
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Appendix A
